The First Commandment (The Scot Harvath Series, Bk. 6)

When the president of the United States is blackmailed into releasing five detainees from Guantanamo Bay, a sadistic assassin with a vendetta years in the making is reactivated. Suddenly, the people closest to counter terrorism operative Scot Harvath are being targeted, and he realizes that somehow, somewhere, he has left the wrong person alive. With his life plunged into absolute peril and the president ordering him to stay out of the investigation, Harvath must mount his own covert plan for revenge - and in so doing uncover shattering revelations about the organizations and the nation he has spent his life serving.